1. Technical Field
The invention relates to tire-building machines for pneumatic tires. More particularly, the invention relates to an elastomeric member or component of the tire-building machine, such as the turn-up bladder, center sleeve or bead lock sleeve, which is subjected to abrasion during operation of the machine when the member is in contact under pressure with a rubber or metal surface during operation of the machine. Even more particularly, the invention relates to a bladder or sleeve having a coat layer of an abrasion-resistant and hard elastomer material bonded on portions of the inner or outer surfaces of the bladder or sleeve to improve bladder and sleeve life by protecting those areas of the member that are subject to abrasion or failure during the building of a pneumatic tire.
2. Background Information
Tire-building machines for the manufacture of pneumatic tires use various elastomeric members, such as a pair of tun-up bladders, adjacent the ends of the machine which, upon inflation, will turn the ends of the carcass plies which have been laid on the tire-building mandrel, up and around the bead rings and back against the ply material These tire-building drums may include a center sleeve or a bead lock sleeve formed of elastomeric material which enables the end segments of the drums to move inwardly, outwardly and radially when forming the toroidal shape of the tire, or to maintain the bead rings in position. These various sleeves and turn-up bladders are subject to abrasion when contacting under pressure certain areas of uncured rubber in the tire components or metal parts, such as the mechanical bead locks or other portions of the tire-building machine, which reduces the life of such a member by wearing certain areas of the sleeve or bladder quicker than other areas. This requires that the sleeves or bladders be replaced more often than desirable, increasing the manufacturing cost for the pneumatic tires. However, it is difficult to adequately guard against the abrasion problems and resulting component failure, especially on the turn-up bladders, since the bladders must remain sufficiently flexible in order to provide the desired turn-up characteristics and performance required for wrapping the carcass ply and carcass ply ends around the bead ring upon inflation.
Another problem with such elastomeric members such as turn-up bladders, is that they are formed of an elastomeric material which has a tendency to stick to the unvulcanized elastomeric green tire components being processed in the machine due to the natural tackiness of these green unvulcanized tire components. This adhesion between the bladder and tire materials can result in unsatisfactory turn-up and undesirable adhesion of the carcass areas around the bead rings. Certain of these problems have been reduced by the use of a release coating and/or a turn-up bladder configuration having externally exposed cords, such as shown in U. S. Pat. Nos. 4,381,331 and 4,853,069.
Other attempts to alleviate such sticking problems involve the use of outside surface coatings on the bladder which are composed of polymer blends of about 10-60 arts polyvinylchloride and about 90-40 parts of an acrylonitrile-butadiene rubber having 25-40 parts acrylonitrile and 60-75 parts butadiene. Such polymer blend coatings are described in U.S. Pat. No. 5,213,823.
Still another proposed solution to such sticking problems involve the use of fabric-covered bladders having their outer surfaces covered with a low adhesive rubber polymer. Such bladders are described in U.S. Pat. Nos. 5,250,142 and 5,324,376.
While such attempts and proposals succeed to greater or lesser extents, the need remains for a turn-up bladder and/or elastomeric sleeve for use on a tire-building drum which have certain areas of the inner or outer surfaces, or both, protected from abrasion by inexpensive and effective means which do not materially affect the flexibility and operation of the elastomeric bladder and/or sleeve.